Method of sealing



Original Filed Jan. 1'7, 1951 FIGZ.

FIGI.

FIGS.

United States Patent METHOD or SEALING Paul S. Sussenbach, Brentwood,Mo., assignor to The Presstite Engineering Company, St. Louis, Mo., acorporation of Missouri Original application January 17, 1951, SerialNo. 2%,353. Divided and this application October 17, 1952, Serial No.315,397

5 Claims. (Cl. 29-526) This invention relates to sealing methods, andmore particularly to a method for sealing around a threaded bolt or thelike extending through openings in bodies to be fastened.

This application is a division of my copending application entitledSealing Member and Method, Serial No. 206,358, filed January 17, 1951.

In securing together two plates or other members by means of a fastener,such as a bolt, it is frequently desirable to seal the opening throughwhich the fastener extends as a preservative against leakage andcorrosion. This invention provides for internal sealing of such openingsin a novel way. The invention utilizes a sealing member comprising arelatively thick apertured member or washer formed of soft, tacky,cold-flow extrudable sealing material. The plasticity of the sealingmember is such that it will maintain its washer-like shape under normalconditions of handling but under pressure will coldflow with permanentdeformation. The devices which are to be fastened with the aid of thewasher are preferably composed of one held member having a relativelysmall opening adjacent the head of a bolt or the like which is to act asa fastener. The other held member has a relatively larger opening overwhich the thick washer is placed, and the soft washer preferably snuglyfits the bolt. Between the soft washer and the nut is a metal washer onthe bolt which is larger in diameter than the soft washer. When the nutis screwed down, it forces the large metal washer against the smaller,thicker, coldflow washer, tending to force it first into said largeropening to in-fill the space around the bolt. The thickness of the softwasher supplies suflicient extrudable material for the above purpose andfor flow out to the edge of the metal washer as a flashing to indicate agood seal. The soft washer is of a consistency that the metal Washer maybe driven into metal-to-metal contact around the relatively largeropening, forcing its way through the material of the soft washer. Thus apermanently tight sealed joint is reliably obtained.

In the finished fastening, one held member and the metal washer are ininterfacial contact, the openings in the held members being filled withsealing material which adheres to the bolt and surrounding parts. Aroundthe fastening is the indicating flashing.

The material from which the sealing washer is formed has certainphysical characteristics that are necessary to the above results.Broadly, the placticity of the sealing material is approximately thatwhich can be hand-molded. The cold-flow characteristic of the materialpermits extrusion of the material from between members forced intointerfacial contact. The material is also tacky to facilitate adherenceand sealing action. For convenient storage and handling beforeapplication, nonadhesive facings are provided on the washer-like sealingmember which are of a nature to disappear during application. Thematerial is also made imperivous to air and'mois ture. Under specialconditions of use, the material may be non-staining, oil-resistant, orit may be vulcanized.

"ice

Materials providing the desired characteristics are unvulcanizedelastomers. Suitable tackifiers, plasticizers and fillers (fibrous andgranular) may be added to the unvulcanized rubber-like component toimprove the physical characteristics of the material. For certain usesit may be desirable further to include antioxidants, adhesives,vulcanizing agents, swelling agents and corrosion inhibitors.

Thus among the objects of the invention are the provision of aneconomical and convenient method adapted for sealing an opening in abody through which extends .a stem-like member; and the provision of amethod of the class described which will result in a rigid rather thanresilient fastening wherein the seal is substantially unaffected by thestresses on the fastener. Other objects will be in part apparent and inpart pointed out hereinafter.

The invention accordingly comprises the steps and sequence of steps, andfeatures of manipulation, which will be exemplified in the methodshereinafter described, and the scope of which will be indicated in thefollowing claims.

In the accompanying drawings, in which several of various possibleembodiments of the invention are diagrammatically illustrated,

Fig. 1 is a top plan view of the washer used in conjunction with thisinvention, with a protective part partially peeled away;

Fig. 2 is a side elevation of Fig. 1;

Fig. 3 is a cross section showing the first step in the method;

Fig. 4 is a View similar to Fig. 3, showing an intermediate step of themethod;

Fig. 5 is a view similar to Figs. 3 and 4, showing the final conditionof the sealed fastener;

Fig. 6 is a fragmentary enlargement of certain parts shown in Fig. 5;and,

Fig. 7 is a view similar to Fig. 4, illustrating an alternative form ofthe invention.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Referring now to the drawings, there is shown a sealing member 1comprising a relatively thick washer formed of soft, tacky, extrudablesealing material 3 and provided with discrete nonadhesive faces 5 and 6composed of a frangible parting material. For this purpose there may beused a thin porous material, such as fragile tissue paper; or the facesmay be dusted with a thin film of talcum powder or the like. The sealingmaterial 3 has a plasticity of an order permitting molding by hand, butis sufficiently stiff to maintain its washer-like shape under normalhandling. Also, the material is relatively inelastic compared tovulcanized rubber. small stress, the sealing material cold flows withpermanent deformation and adheres to surfaces which it engages. The useof this sealing member is described in connection with a bolt thatfastens together a pair of plates, although the member may be used toseal around any stem-like element extending through openings in anybodies to be fastened.

Referring to Fig. 3, there is shown a body 7 in the form of a flat rigidmetal plate, which is to be fastened to another plate 9 by means of abolt 11. The bolt has a threaded stem or shank 13 extending through and'projecting from suitable openings 15 and 17 in the plates 7 and 9,respectively. Opening 15 is larger than opening 17. Between the stem 13and plates 7 and 9are voids 19. The sealing member 1 snugly fits thestem 13 of' When subjected even to sealing member. It is larger indiameter than opening 15. The inside diameter of a metal washer usuallyis in. greater than the outside diameter of the bolt. It is desirablefor the sealing member to have a close fit with the bolt, in order tofacilitate sealing action, and the plastic property of the sealingmember permits it to be fitted over the bolt even where the fit isclose. In some instances, however, it is desirable for the sealingmember 1 to have a loose fit with the bolt in order to facilitate fastassembly of the parts. It is important that the outside diameter of themetal Washer 21 should be larger than the outside diameter of thesealing member 1, so that the former overlaps the latter. The thicknessand outside diameter of the sealing member are primarily determined bythe amount of sealing material required to fill voids between the stem13 and plates 7 and 9. In a standardized set of sealing members, theinside diameter might vary in steps of in., the outside diameter mightbe /8 in. greater than the inside diameter, and a choice of thicknessesof in. or A; in. might be provided.

Fig. 3 illustrates the assembly of parts with a threaded fastenerelement or nut 23 threaded lightly down upon the metal washer 21. As thenut is screwed down further, the plate 7 and metal washer 21 are forcedtogether with squeezing effect upon the sealing member 1 therebetween.The material 3 of the sealing member is relatively incompressible ascompared to its ready tendency to flow, hence a cold extrusion of thematerial 3 results (Fig. 4). The extrudable sealing material is forcedfrom between members 7 and 21, and into the voids 19 around the stem 13of the bolt. Much of the flow of sealing material is inward, because theportions of members 7 and 21 that overlap the sealing member offerinitial resistance to outward flow of the sealing material.

As shown in Figs. 5 and 6, the rigid metal washer 21 is finally forcedinto a metal-to-metal or interfacial engagement 25 with the rigid metalplate 7, and substantially all of the material 3 is forced from betweenthese fiat rigid members 7 and 1. This interfacial engagement of themembers 7 and 21 permits a rigid fastening of the plates 7 and 9. Thenut 23 may thus be tightened to provide as tight a fastening as would bepossible without the sealing member. Ordinarily, the surfaces of members7 and 21 will not be accurately flat and smooth, hence some sealingmaterial may remain to fill the irregularities between these surfaces,while other substantial portions of the surfaces are in direct contactto provide a rigid fastening. It will be understood that the surfaceirregularities shown in Fig. 6 are merely intended to be those inherentin typical commercial structural members and fastener elements.

The sealing material 3 offers inappreciable resistance to threading downthe nut, and the increase in torque required to thread down the nut overthat required Without a sealing member is slight, being of the order offour ounce-inches in a normal case.

The feature that the member 1 has substantial coldflow characteristicswithout substantial resilience is important, since it allows the statedface-to-face contact between the washer and a member such as 7, besidesthe extrusive in-filling around the threads of the bolt 11. Withordinary sealing washers composed of resilient material such as rubber,a sealed and tight fastening may be obtained for some time, butultimately it will deteriorate as the material loses its resiliency andtakes a set. The ordinary result then is both leakage and a loose joint.By means of the present invention the material of the member 1 does notcontribute at all to the reactions which hold the joint tight, since itis squeezed out almost entirely from between the faces of 21 and 7. Theentire holding reaction is thus due to the metal-to-metal contactbetween the members 21 and 7, and this reaction never deteriorates,whether or not the sealing material takes a set. In fact, in some cases,as will appear, an immediate set is encouraged.

The head 27 of the bolt 11 and the nut 23 confine the flow of sealingmaterial along the bolt, and thus determine the voids 19 into which thesealing material may flow. If the quantity of material 3 (determined bythe dimensions of the sealing member) extruded inward is more thansufiicient to fill the available voids, some compression of the sealingmaterial in the void may occur at this point, provided the sealingmaterial is compressible. If the material 3 is incompressible, then theexcess material, initially tending to flow inward, is finally alsoextruded outward from beneath the metal washer 21 and forms a small lipportion 22 around the periphery of the washer. This lip acts as a signalthat the joint is in-filled and that a proper size of sealing member isbeing used. Extrusion to a point beneath the nut 25 or beneath the head27 of the bolt 11 is substantially prevented by the high frictionalresistance presented to such flow.

In the extrusion process, the thin porous faces 5 and 6 on the sealingmember are mashed and largely absorbed, so that the sealing materialcomes into direct contact with and adheres to the metal surfaces, withno intervening tissue. Thus, the soft, tacky extrudable sealing materialnot only fills the voids, but also adheres to the surfaces enforced. Theflow of sealing compound for the Fig. 7

embodiment is otherwise the same as that described heretofore. Fig. 7illustrates the conical washer 29 as only partially flattened out,although it will be understood that the washer is finally practicallyflattened in order to provide the most rigid fastening.

As pointed out above, the sealing material 3 of the sealing member 1 hascertain physical characteristics. The material is impervious to air,dust and moisture in order to be an effective sealing medium, and istacky so that it adheres to the members which are to be sealed. Also,the material is readily extruded in order to fill voids which are to besealed, the elasticity of the material being sufliciently low to permitcold flow. A slight elasticity is not objectionable so long as it doesnot interfere with the primary extrusion properties of the material.Finally, the material should not deteriorate over very long periods.

Suitable materials with which to make the sealing member areunvulcanized elastomers, including rubber. The physical and chemicalcharacteristics of the elastomers may be improved by mixing otheringredients, such as plasticizers, tackifiers and fillers, fibrous andgranular.

These latter ingredients improve the extrusion of the material and giveit strength and body so that it will maintain the desired washer-likeshape prior to use.

The following examples illustrate the invention.

Example 1 A material from which sealing members used in the presentinvention are formed is made of the following components:

5 Example 1-Continued Parts by weight Antioxidant--Trimethyl dihydroxyquinoline (obtainable under the trade-name Agerite Resin D) 0.3Fillercarbon black of the semi-reinforcing furnace type (obtainableunder the trade-name Thermax) 2.9 Fillerpulverized tree bark, 28 mesh(obtainable under the trade-name 508 Silvacon) 11.6 Fillerpulverizedtree bark, 100 mesh (obtainable under the trade-name 490 Silvacon) 11.6

This material was tested for plasticity and consistency and according tothe standard ASTM (American Society for Testing Materials) D5-49 Testfor bituminous materials it gave a needle penetration of 3.5 mm. at 77F. The test differed from standard procedure only in that the materialwas packed into the test container instead of being poured in.

The proportions of the components in the above example may be variedconsiderably and the limits in percent by weight are as follows: Boththe elastomer and the tackifier and elastomer may be varied between 5%to 40%. The plasticizer and extender may be varied between to 60% andthe antioxidant between 0% and 2%. The carbon black filler may be variedbetween 0% to 15% while the other two fillers may be varied between 5%to 30%. Also, any polyisobutylene having a molecular weight between 7000to 15,000 is suitable.

Example 2 LMMS) 49.0 Fillerchrysolite asbestos fibers 18.0Fillerchrysolite asbestos floats 32.0 Waterproofing agent-aluminumdistearate 1.0

This material was tested by the ASTM D5-49 Test and a needle penetrationof 3.5 to 6.0 mm. was obtained. In this example the plasticizer andextender were omitted. The waterproofing agent serves to close the poresof the fibrous filler. This material is non-staining and odorless andmay be painted.

, The proportions of the components in the above example can be variedconsiderably and the limits in percent by weight are as follows: Theelastomer and tackifier component may be varied between 30% and 50%. Theasbestos fiber filler may be varied between and 50% while the asbestosfloat filler may be varied between and 40%. The Waterproofing agent maybe present in percentages between 0.5% and 2%. Also, any metallic soapmay be used in place of the aluminum distearate.

Example 3 Vulcanizing agent-sulfur 0.55 Acceleratortetramethyl thiuramdisulfide (obtainable under the trade-name Methyl Tuads) 0.05

' corrosion inhibltor may vary between 0% and 5%.

Accelerator-mercaptobenzo thiazole (obtainable Needle penetration by theASTM D5-49 Test was between 6.0 and 9.0 mm.

This material may be vulcanized by application of heat after the sealhas been made and the material extruded into the voids 19. The soft,tacky material is thereby changed to an expanding, tough, resilient,substance. The adhesive greatly improves the bond between the metalparts being sealed after vulcanizing because it is a thermosettingresin. Prior to vulcanizing, the adhesive acts as a filler.

The proportions of the components in the above example may be variedconsiderably and the limits in percent by weight are as follows: Theelastomer may be present in amounts between 20% and 60%, and theplasticizer and extender in amounts between 20% and 40%. The adhesivemay vary in quantities between 10% and 20%. The vulcanizing agent may bepresent in amounts as low as .1% and as high as 1.0%. The disulfide andthiazole accelerators may each vary between .01% and 1.0%. Both theaccelerator activator and filler and the antioxidant components may varybetween 1% and 3%, while the accelerator retarder is present inproportions between .1% and .3%. Other metallic oxides than zinc oxideare useful as accelerator activators and fillers.

Example 4 Example 3 was repeated except that the percentage of theelastomer was reduced to 55.0% and a swelling agent, diazoamino benzene(obtainable under the trade-name Unicel), was added in the amount of2.7% by weight. The ASTM D5-49 Test gave the same result as in Example3. This material was also vulcanized after the seal was made to changethe physical nature of the sealing material to a resilient condition.There was more expansion during the vulcanizing operation than with thematerial of Example 3.

The same variations in proportions of components is permissible in theabove example as was listed in Example 3, the swelling agent of thisexample being present in amounts between 1% to 3%.

Example 5 A material from which sealing members used in the presentinvention are formed is made of the following components:

The needle penetration in accordance with the ASTM D549 Test was between5.0 and 10.0 mm. In this example it will be noted that the ingredients,particularly the elastomer, are oil-resistant.

The proportions of the components in the above example may be variedconsiderably and the limits in percentage by weight are as follows: Theelastomer may be varied between 30% and The plasticizer may be presentin amounts between 1% and 5%. The filler may compose between 25% and 50%of the material and the The unvulcanized elastomers have some degree ofplasticity, which may be increased by the plasticizers or decreased bythe solid fillers. In the first four examples, the plasticizer has asubstantial filling effect. Also, the

unvulcanized elastomers have a tacky property, and this is increased bythe tackifiers or decreased by the extenders and fillers. An adhesiveeffect may also be obtained by the use of a setting adhesive, as shownin Example 3. Antioxidants and corrosion inhibitors are desirable toprevent rusting of the metal parts with which the sealing material comesin contact and to preserve the elastomer. Where it is desirable, thesealing material of Examples 3 and 4 may be vulcanized. The vulcanizingheat may be supplied in any suitable manner to the metal partscontaining the sealing material. Inasmuch as the sealing material isconfined by the metal parts, expansion of the material resulting fromthe vulcanizing will tend to improve the seal.

The above materials are formed into the described washer-like sealingmembers and the nonadhesive facings 5 adhered thereto. These facings maybe of porous tissue paper, or of a similar nature, their principalpurpose being to prevent several stacked sealing members from adheringto one another or to the hands of a user. But they must be of a naturesuch as to disintegrate under pressure, the resulting particles to beengulfed or surrounded by the plastic material during cold flow.

In conclusion, the invention features the provision of a sealing memberin the shape of a relatively thick washer formed of soft flowablematerial which in use is placed over a bolt or the like and between apair of relatively rigid apertured plates and compressed thereby tocause the sealing material to flow around the bolt and completely sealit within the apertured plates. It will be understood that metal Washerssuch as shown in Figs. 36 need not be employed, but that the sealingmember may be placed between two structural members, such as 9 and 11.Also, the fastener need not be a bolt but may be any other type ofsimilar fastener, such as a screw, rivet or the like, the importantfeature being that the metal plates be brought into interfacial contact,with the sealing material substantially forced from between the platesso that the material does not carry the stress on the fastening requiredfor keeping it tight.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above methods without departingfrom the scope of the invention, it is 4 intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

I claim:

1. The method of sealing the stem of a headed fastener extending throughan opening in a body and projecting from one side of the body,comprising the steps of applying a Washer-like sealing member of soft,tacky extrudablc sealing material to surround the stem with one face ofthe sealing member engaging said side of the body around the openingtherein, applying an apertured member larger than the sealing member tothe stem having a pressure face engaging the other face of the sealingmember, said pressure face being adapted for flatwise engagement withthe said side of the body around the opening therein, and forcingtogether the body and apertured member to the point Where the saidpressure face of the apertured member comes into flatwise engagementwith the said side of the body, the volume of the sealing member beinggreater than the volume of the space in the opening in the body aroundthe stem and the space in the aperture of said apertured member aroundthe stem, the material of the sealing member being extruded into andfilling said spaces and the excess thereof being substantially entirelyforced out from between the pressure face of the apertured memher andthe said side of the body to form a flashing around the aperturedmember, the material extruded into said spaces adhering to the stem, thebody and said apertured member.

2. The method of sealing the shank of a bolt extending through anopening in a body and projecting from one side of the body, comprisingthe steps of applying a washerlike sealing member of soft, tackyextrudable sealing material to surround the shank with one face of thesealing member engaging said side of the body around the openingtherein, applying a metal washer of greater diameter than the sealingmember to the shank having a pressure face engaging the other face ofthe sealing member, said pressure face being adapted for flatwiseengagement with the said side of the body around the opening therein,and threading a nut on the shank to force together the body and metalwasher to the point Where the said pressure face of the washer comesinto flatwise engagement with the said side of the body, the volume ofthe sealing member being greater than the volume of the space in theopening in the body around the shank and the space in the opening in thewasher around the shank, the material of the sealing member beingextruded into and filling said spaces and the excess thereof beingsubstantially entirely forced out from between the pressure face of thewasher and the said side of the body to form a flashing around thewasher, the material extruded into said spaces adhering to the shank,the body and the washer.

3. The method of claim 2 wherein the washer is initially flat.

4. The method of claim 2 wherein the washer is initially conical and isflattened by the nut.

5. The method of fastening two metal members comprising inserting aheaded bolt through bolt holes in the members, the head of the boltengaging one member and its shank projecting from the other, applying awasherlike sealing member of soft, tacky extrudable sealing material tosurround the shank with one face of the sealing member engaging saidother metal member around the bolt hole therein, applying a metal washerof greater diameter than the sealing member to the shank of the bolthaving a pressure face engaging the other face of the sealing member,said pressure face being adapted for flatwise engagement with the saidother metal member around the bolt hole therein, threading a nut on thebolt to force together the metal members and washer to the point wherethe said pressure face of the washer comes into flatwise engagement withthe said other metal member, the volume of the sealing member beinggreater than the volume of the space in the bolt holes around the shankand the space in the opening in the Washer around the shank, thematerial of the sealing member being extruded into and filling saidspaces and the excess thereof being substantially entirely forced outfrom between the washer and said other metal member to form a flashingaround the washer, the material extruded into said spaces adhering tothe shank, said metal members and the washer.

References Cited in the file of this patent UNITED STATES PATENTS642,411 Allen Jan. 30, 1900 1,013,017 Howarth Dec. 16, 1911 1,515,996Buchanan Nov. 18, 1924 1,942,489 Pfefferle Jan. 9, 1934 2,097,713 AshleyNov. 2, 1937 2,250,343 Zigler July 22, 1941 2,286,668 Brooke June 16,1942 2,379,804 Johnson July 3, 1945 2,416,548 Schaul Feb. 25, 1947

